This invention relates to a unitary frame and fluid driven unitary cartridges useful in an ultra high-pressure, high-temperature, press apparatus. More particularly, this invention relates to a reduced mass, multi-axis, ultra-high pressure, high temperature, hydraulically actuated, press apparatus capable of reaching pressures in excess of 35 kilobars and temperatures above 1000 degrees centigrade. Such a press is useful in the production and sintering of superhard materials such as cemented ceramics, diamond, polycrystalline diamond, cubic boron nitride, and exotic metallodial gases such as metallic hydrogen.
Multi-axis, ultra high-pressure, high-temperature, presses have been known in the art for the production and sintering of superhard materials for more than three decades. They may be classified by the tonnage of pressure, or xe2x80x9cthrust,xe2x80x9d they are capable of exerting on the reaction cell. For example, a 2000-ton multi-axis press is capable of producing approximately 700,000 p.s.i on each face of a cubic reaction cell, which is a force sufficient to produce a superhard payload such as diamond, polycrystalline diamond, or cubic boron nitride. FIG. 14 depicts a conventional multi-axis press that was patented by Dr. H. Tracy Hall, the inventor of reproducible man-made diamond. See U.S. Pat. Nos. 2,918,699 and 3,913,280. Basically, there are five components in this press design: the tie-bar frame (44), the massive bases (45) supporting he tie-bar frame, the piston cylinders (46), the guide pins (47), and the anvils (48). Because the bending moments of the tie bar press are so great, its mass becomes enormous as the size of the press is increased. For example, the weight of a 3000-ton tie bar style steel press may exceed 60 tons, in order to withstand the reaction forces produced by the hydraulic pistons. The weight of a 4000-ton tie bar steel press is known to exceed 100 tons. Because the bending moments are so great, the bases of a 4000-ton tie bar press experience occasional fatigue failures.
Since man-made diamond was first produced in a G.E. laboratory by Dr. Hall, circa 1953, the commercial production, and sintering of diamond and other superhard materials has become a multi-billion dollar industry worldwide. Modern production of superhard materials continues to increase at a growth rate of 15 percent, or more, annually. But despite the success of the superhard industry, given their unique properties, diamond and other superhard materials have barely scratched the surface of their potential commercial applications. In order for superhard materials to reach their full commercial potential, more economical and more efficient multi-axis presses must be designed and constructed to satisfy the ever increasing demand for these modern miracle materials.
Typically, the manufacturing or sintering process for superhard materials in a multi-axis press consists of placing a superhard payload inside a high-pressure, high-temperature, reaction cell known in the art The reaction cell, made up of a pressure-transferring medium also known in the art, is placed within the press""s high-pressure chamber and subjected to an ultra-high compressive force. During the press cycle, the pressure inside the cell must reach 35 kilobars, or more. Simultaneously, an electrical current is passed through the cell""s resistance heating mechanism, also known in the art, raising the temperature inside the cell to above 1000xc2x0 C. Once the superhard payload is subjected to sufficient pressure and temperature for a prescribed period of time, the current is terminated and the cell cooled. Pressure on the cell is then released, the anvils retracted, and the cell with its superhard payload removed from the press. The four aspects, then, of the multi-axis press cycle are: 1) to exert sufficient force on the cell, creating internal pressures above 35 kilobars, 2) to raise the temperature inside the cell to above 1000xc2x0 C., 3) to cool the cell quickly; and 4) to release the force on the cell and retrieve the payload from the press.
The cost of construction of a multi-axis press is proportional to its mass and while its efficiency is proportional to the duration of its cycle and volume of its payload. Therefore, the smaller the mass of the press, and the shorter the duration of the pressing cycle, and the larger the cell, permitting a larger volume of payload, the higher the economy and efficiency of the multi-axis press. These parameters presented significant engineering and design challenges to the inventor herein in reaching his objective of producing or sintering superhand materials more efficiency and more economically in a multi-axis press.
The inventor""s first objective in making the prress more efficient was to come up with a more compact press frame design. His aim was a press with less mass: one that would not exhibit the bending moments of the tie-bar frame, which limited the size of the press and its payload capacity.
intuitively for the design, the inventior settled upon a unique single-piece frame, which eliminated the tie bars, centralized the frame""s mass, and permitted the use of internally intensified, unitary, piston cylindres. Surprisingly, he discovered that by using this unitary frame and cylinder design, he was able to achieve a significant reduction in the overall size and weight of the press. This made the press more economical to build and reduced the cost of payload produced per ton of press.
Next, by using an innovative internal intensifier piston within a unitary cylinder, the inventor discovered that he could reduce even more the overall size and cost of the press. In the conventional tie-bar press system, the length and diameter of the piston cylinders are proportional to the overall size of the press, and the hydraulic fluid must be pumped to the press at pressures around 10,000 p.s.i., or more, which requires specially made high-pressure pumps, hoses, and fittings. In the press of the present invention, on the other hand, the length and diameter of the piston cylinders are not proportional to the size of the press, resulting in a more compact overall design. And since fluid pressure amplification occurs inside the piston cylinder, the high pressure at which fluid needs to be pumped to the press may be reduced by up to one half, eliminating the need for the specially made high-pressure pumps, hoses, and fittings.
In designing the unitary cartridge with internal intensification, the inventor relied upon a hydraulic model based upon a standard hydraulic fluid used in the conventional tie-bar press""s piston cylinder. In attempting to operate his new press, however, the inventor was surprised to discover that the standard hydraulic fluid used in the conventional press was not stiff enough for his new design, and the internal intensifier piston bottomed out without applying sufficient force on the cell. To overcome this obstacle, the inventor selected a water glycol based energy transmitting fluid, having a bulk modulus greater than 370,000 psi, such as that manufactured by Union Carbide, U.S. Pat. No. 4,855,070. To his surprise, in the press cartridge this fluid seemed to exhibit properties of stiffness greater than its constituent compounds as reported by its manufacturer, which resulted in an intensifier piston stroke even shorter than anticipated.
The inventor also discovered that because of the fluid""s high stiffness, it stored less energy. This is significant because during the pressing cycle, the fluid is compressed within the cartridge and stores spring like energy. In the event of a catastrophic loss of pressure during the pressing cycle, known in the art as a xe2x80x9cblow out,xe2x80x9d this stored energy suddenly escapes creating tremendous torsional loads on the press components. Such loads are so great that they can actually tender the press inoperable. Therefore, the less stored energy in the fluid, the less likely damage will result to the press from a blowout.
An additional objective of the inventor in was to increase the volume of the reaction cell""s payload. This he was able to achieve in the new unitary press design by use of a rectangular prismatic cell. Since the cartridges of the present invention are capable of functioning independently of each other, they are then capable of exerting differential forces on the sides of the cell while producing the uniform internal pressure required in the manufacturing process. This permits the use of a prismatic reaction cell. By utilizing a prismatically configured high-pressure chamber and rectangular reaction cell, the volume of the payload may be increased three fold. This increased volume translates into higher production rates and less cost per unit of product, hence greater efficiency and economy in the manufacturing process.
In the art, superhard materials are manufactured by assembling the product to be produced inside a reaction cell, by placing the reaction cell in the high-pressure chamber of a high-pressure press, and by simultaneously compressing the cell to ultra high pressure while passing an electrical current through the cell""s resistance heater mechanism, which raises the temperature inside the cell to above 1000xc2x0 C. It is the object of this invention to utilize known reaction cell technology in an innovative press in order to produce superhard materials economically and efficiently. This will be achieved in the present invention by utilizing an innovative reduced mass unitary press frame, requiring a mass of less than 12 tons of steel for a 3000-ton press, and unitary cartridge bodies having an internal fluid pressure intensifier requiring less than 5000 p.s.i. external pump pressure. A 3000-ton steel press of the present invention weighs less than 30 tons compared to a conventional tie-bar style steel press weighing in excess of 60 tons. Similar or greater mass reductions are achievable as the press size is increased. For example, an 8000-ton steel press can be produced weighing less than 50 tons.